Add patches to build webrtc with external OpenSSL.

webrtc_libsrtp.diff

@@ -0,0 +1,27 @@
+diff --git a/BUILD.gn b/BUILD.gn
+index 6359585..0c9d2ff 100644
+--- a/BUILD.gn
++++ b/BUILD.gn
+@@ -3,6 +3,7 @@
+ # found in the LICENSE file.
+ 
+ import("//testing/test.gni")
++import("//webrtc.gni")
+ 
+ declare_args() {
+   # Tests may not be appropriate for some build environments, e.g. Windows.
+@@ -114,9 +115,11 @@ static_library("libsrtp") {
+     "srtp/ekt.c",
+     "srtp/srtp.c",
+   ]
+-  public_deps = [
+-    "//third_party/boringssl:boringssl",
+-  ]
++  if (rtc_build_ssl) {
++    public_deps += [ "//third_party/boringssl" ]
++  } else {
++    configs += [ "//rtc_base:external_ssl_library" ]
++  }
+ }
+ 
+ if (build_libsrtp_tests) {

webrtc_src.diff

@@ -0,0 +1,26 @@
+diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
+index 0805a5c549..6150fdaaa9 100644
+--- a/rtc_base/BUILD.gn
++++ b/rtc_base/BUILD.gn
+@@ -24,6 +24,7 @@ if (!rtc_build_ssl) {
+     assert(rtc_ssl_root != "",
+            "You must specify rtc_ssl_root when rtc_build_ssl==0.")
+     include_dirs = [ rtc_ssl_root ]
++    libs = rtc_ssl_libs
+   }
+ }
+ 
+diff --git a/webrtc.gni b/webrtc.gni
+index 64a170c23f..044529a689 100644
+--- a/webrtc.gni
++++ b/webrtc.gni
+@@ -85,6 +85,9 @@ declare_args() {
+   # library that comes with WebRTC (i.e. rtc_build_ssl == 0).
+   rtc_ssl_root = ""
+ 
++  # Used to specify an external OpenSSL libs.
++  rtc_ssl_libs = []
++
+   # Selects fixed-point code where possible.
+   rtc_prefer_fixed_point = false
+ 

webrtc_third_party.diff

@@ -0,0 +1,23 @@
+diff --git a/usrsctp/BUILD.gn b/usrsctp/BUILD.gn
+index 014a076aec3..2d7daeba03a 100644
+--- a/usrsctp/BUILD.gn
++++ b/usrsctp/BUILD.gn
+@@ -3,6 +3,7 @@
+ # found in the LICENSE file.
+ 
+ import("//build/toolchain/toolchain.gni")
++import("//webrtc.gni")
+ 
+ config("usrsctp_config") {
+   include_dirs = [
+@@ -140,5 +141,9 @@ static_library("usrsctp") {
+   if (is_fuchsia) {
+     defines += [ "__Userspace_os_Fuchsia" ]
+   }
+-  deps = [ "//third_party/boringssl" ]
++  if (rtc_build_ssl) {
++    deps += [ "//third_party/boringssl" ]
++  } else {
++    configs += [ "//rtc_base:external_ssl_library" ]
++  }
+ }